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Shell Limestone
Shelly limestone is a highly fossiliferous limestone, composed of a number of fossilized organisms such as brachiopods, bryozoans, crinoids, sponges, corals and mollusks. It varies in color, texture and hardness. Coquina is a poorly indurated form of shelly limestone. Shelly limestone is a sedimentary rock because it is made up of fragments. To be shelly, it is full of broken shells which are "glued" together with calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on .... Calcium carbonate often makes up around 10% of the volume, whilst many varied sized shells from granular to very large pebbles. Its color is gray. Formation Each shelly limestone is unique in its own way, where every stone of this type is composed of different fossilized organism and shell fragments. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coquina
Coquina () is a sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically sorted fragments of the shells of mollusks, trilobites, brachiopods, or other invertebrates. The term ''coquina'' comes from the Spanish word for " cockle" and "shellfish". For a sediment to be considered to be a coquina, the particles composing it should average or greater in size. Coquina can vary in hardness from poorly to moderately cemented. Incompletely consolidated and poorly cemented coquinas are considered grainstones in the Dunham classification system for carbonate sedimentary rocks. A well-cemented coquina is classified as a biosparite (fossiliferous limestone) according to the Folk classification of sedimentary rocks. Coquinas accumulate in high-energy marine and lacustrine environments where currents and waves result in the vigorous winnowing, abrasion, fracturing, and sorting of the shells that compose them. As a result, they typi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Precambrian Era
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time. The Precambrian is an informal unit of geologic time, subdivided into three eons (Hadean, Archean, Proterozoic) of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago ( Ga) to the beginning of the Cambrian Period, about million years ago ( Ma), when hard-shelled creatures first appeared in abundance. Overview Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earth's history, and what is known has largely been discovered from the 1960s onwards. The Precambrian fossil re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes, such as the accumulation of corals and shells in the sea, have likely been more important for the last 540 million years. Limestone often contains fossils which provide scientists with information on ancient environments and on the evolution of life. About 20% to 25% of sedimentary rock is carbonate rock, and most of this is limestone. The remaining carbonate rock is mostly dolomite, a closely related rock, which contains a high percentage of the mineral dolomite, . ''Magnesian limestone'' is an obsolete and poorly-defined term used variously for dolomite, for limes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Types Of Limestone
This is a list of types of limestone arranged according to location. It includes both formal stratigraphic unit names and less formal designations. Africa Egypt *Tura limestone, used for the Great Pyramid casing stones *Mokattam limestone; Great Pyramid core stones and head of the Great Sphinx are of the "Member III" stratum * Galala marble (a type of limestone, not a true marble) Asia India * * Israel (West Bank) * * Europe Austria * Belgium *, (not a "true marble"; Devonian limestone) * * Croatia * France * *, or "Paris stone" (city buildings are widely faced with it) **, or Oise, limestone (variety of Lutetian) * *, in the Loire Valley Germany * * Gibraltar * Ireland * , not a "true marble"; fossiliferous Carboniferous limestone. Italy * , not a "true marble"; fossiliferous limestone United Kingdom England: * (not a "true marble"; Carboniferous limestone) * * * , the famous London Stone is made of this. * (not a "true slate"; thin-bedded limestone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diagenesis
Diagenesis () is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a role as sediments become buried much deeper in the Earth's crust. In the early stages, the transformation of poorly consolidated sediments into sedimentary rock (lithification) is simply accompanied by a reduction in porosity and water expulsion (clay sediments), while their main mineralogical assemblages remain unaltered. As the rock is carried deeper by further deposition above, its organic content is progressively transformed into kerogens and bitumens. The process of diagenesis excludes surface alteration (weathering) and deep metamorphism. There is no sharp boundary between diagenesis and metamorphism, but the latter occurs at higher temperatures and pressures. Hydrothermal solutions, meteoric groundwater, rock porosity, permeability, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on Scratch hardness, scratch hardness comparison. Large calcite crystals are used in optical equipment, and limestone composed mostly of calcite has numerous uses. Other polymorphs of calcium carbonate are the minerals aragonite and vaterite. Aragonite will change to calcite over timescales of days or less at temperatures exceeding 300 °C, and vaterite is even less stable. Etymology Calcite is derived from the German ''Calcit'', a term from the 19th century that came from the Latin word for Lime (material), lime, ''calx'' (genitive calcis) with the suffix "-ite" used to name minerals. It is thus etymologically related to chalk. When applied by archaeology, archaeologists and stone trade pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indurated
Friability ( ), the condition of being friable, describes the tendency of a solid substance to break into smaller pieces under duress or contact, especially by rubbing. The opposite of friable is indurate. Substances that are designated hazardous, such as asbestos or crystalline silica, are often said to be friable if small particles are easily dislodged and become airborne, and hence respirable (able to enter human lungs), thereby posing a health hazard. Tougher substances, such as concrete, may also be mechanically ground down and reduced to finely divided mineral dust. However, such substances are not generally considered friable because of the degree of difficulty involved in breaking the substance's chemical bonds through mechanical means. Some substances, such as polyurethane foams, show an increase in friability with exposure to ultraviolet radiation, as in sunlight. Friable is sometimes used metaphorically to describe "brittle" personalities who can be "rubbed" by seemingl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mollusk
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species. The proportion of undescribed species is very high. Many taxa remain poorly studied. Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater and terrestrial habitats. They are highly diverse, not just in size and anatomical structure, but also in behaviour and habitat. The phylum is typically divided into 7 or 8 taxonomic classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known invertebrate species. The gas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton. A coral "group" is a colony of very many genetically identical polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in height. A set of tentacles surround a central mouth opening. Each polyp excretes an exoskeleton near the base. Over many generations, the colony thus creates a skeleton characteristic of the species which can measure up to several meters in size. Individual colonies grow by asexual reproduction of polyps. Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously overnight, often around a full moon. Fertilized eggs form planulae, a mobile early form of the coral polyp which, when m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
